Method for manufacturing sustained-release matrix-type granular complex fertilizer and matrix-type granular complex fertilizer obtained therefrom

ABSTRACT

Disclosed herein are matrix-type, controlled-release granular compound fertilizer and a method for preparing the same. The method comprises: mixing a natural or synthetic polymer as a binder with a nutrient-absorbent, bulking agent to give a mixture, and drying and pulverizing the mixture to afford a nutrient-absorbent supplement; and evenly blending the nutrient-absorbent supplement with a fertilizer ingredient and drying the blend.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is a matrix-type, controlled-release compoundfertilizer exhibiting high use efficiency, and a method for preparingthe same. More particularly, the present invention relates tomatrix-type, controlled-release granular compound fertilizer thatemploys a nutrient-absorbent bulking agent to retain fertilizeringredients over a long period of time and to release the fertilizeringredients in a controlled manner, unlike conventional coated forms,thereby enhancing the use efficiency of fertilizer by plants, with aminimum loss, and a method for preparing the same.

2. Description of the Related Art

In the agricultural field, various fertilizers including solid granularfertilizers, liquid fertilizers, immediate-release fertilizers, andslow-releasing fertilizers have been developed and applied. Inter alia,slow-releasing fertilizers in which particles of fertilizing ingredientsare coated with a polymer are predominantly used. However, coatedfertilizers are likely to remain for a long period of time in soil whenthe coat is not degraded. In addition, since coated fertilizers areprepared using an expensive facility, such as a fluidized bed coater, adrum coater, etc., they are expensive and thus are not widely utilized.Despite these disadvantages, coated fertilizers have recently attractedkeen attention as labor-saving fertilizers, which serve to mitigate thedeclining number of farmers, because they are slowly dissolved over along period of time to reduce the number of required applications.

Korean Patent Application Unexamined Publication No. 19960022408Asuggests a method of slowing the dissolution rate of fertilizingingredients in which a mixture of a resin and a fertilizer is extrudedthrough an extruder to coat the fertilizing ingredients with the resin.However, the fertilizer is problematic in terms of commercializationbecause the method requires the use of a large amount of the expensiveresin.

Korean Patent No. 10-0850186 discloses a fertilizer compositioncontaining poly aspartic acid as potentiator for increasing theutilization efficiency of the fertilizer provided to plants, and amethod for preparing fertilizer comprising the addition of polyasparticacid in an amount of 0.1 to 10% to compound fertilizer so as to increasethe utilization efficiency of the fertilizer. The compound fertilizerprepared by this method is observed to increase in utilizationefficiency because polyaspartic acid suppresses the leaching offertilizer ingredients. However, it does not enjoy a labor-saving effectsince plants need an application of supplementary fertilizer thereto.

U.S. Pat. No. 6,749,659 introduces a matrix concept to delay thedissolution of ammonium sulfate in water wherein the matrix is composedof elemental sulfur and swelling clay. The fertilizer granule isprepared by blending a fertilizer material into a liquefied mixture ofsulfur and swelling clay and granulating the blend. Dissolution rates ofthe fertilizer granule depend on granule sizes, with the rate of releaseof 1 to 2 mm particles doubling that of 2 to 4 mm particles. Themechanism of controlled release of this fertilizer seems to beelectrostatic interaction between negatively charged clay and ammoniumions, thereby suppressing the release of fertilizer materials.

Chinese Patent No. 101857490A discloses a compound fertilizer capable ofcontrolling release rates of fertilizing ingredients. Thecontrolled-release compound fertilizer is prepared by spraying aliquefied mixture of a fertilizing ingredient and a swellable humectantclay, called attapulgite, from the top of a tower-type granulator. Thismethod, although obtaining controlled release, is complex and requiresinvestment for a new facility

U. S. Pat. No. 7,252,697 B2 discloses a method for makingcontrolled-release ammonium phosphate fertilizer. This method comprisesmixing an ammonium phosphate slurry with a clay mineral such as zeolite,montmorillonite, etc.; acidifying the mixture with sulfuric acid; andgranulating the acidified mixture. In this patent, however, there are nocontents of controlled release, but only enhancement of the useefficiency of phosphate by preventing the fixation of phosphate in soil.

Leading to the present invention, intensive and thorough research intocontrolled-release compound fertilizer resulted in the finding thatfertilizer, when prepared in a matrix-type granular form by combining abulking agent showing high nutrient uptake with a binder to give asupplement, and evenly mixing the supplement with compound fertilizer,can be produced using a general production facility for compoundfertilizer and that the matrix-type granular compound fertilizer canabsorb and retain nutrients for a long period of time so that theabsorbed nutrients are resistant to leaching in soil and runoff, therebyincreasing the use efficiency of fertilizer by plants.

DOCUMENTS OF RELATED ART

Patent document 1: Korean Patent Application Unexamined Publication No.19960022408 A

Patent document 2: Korean Patent No. 10-0850186

Patent document 3: U. S. Pat. No. 6,749,659B1

Patent document 4: CN 101857490A

Patent document 5: U. S. Pat. No. 7,252,697B2

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a methodfor preparing matrix-type, controlled-release granular compoundfertilizer using a nutrient-absorbent bulking agent.

It is another object of the present invention to provide the matrix-typecontrolled-release granular compound fertilizer prepared by the method.

In accordance with an aspect thereof, the present invention provides amethod for preparing matrix-type, controlled-release, granular compoundfertilizer, comprising:

mixing a natural or synthetic polymer as a binder with anutrient-absorbent bulking agent to give a mixture, and drying andpulverizing the mixture to afford a nutrient-absorbent supplement; and

evenly blending the nutrient-absorbent supplement with a fertilizeringredient and drying the blend.

For use in the method for the preparation of matrix-type,controlled-release granular compound fertilizer, the polymer ispreferably composed of at least two selected from the group consistingof: polyacrylamide, polyvinylacetate, polyvinyl acetate copolymer(-ethylene), polyvinyl alcohol and a polyvinyl alcohol copolymer, ethylcellulose, methyl cellulose, hydroxymethyl cellulose, hydroxypropylcellulose, hydroxymethylpropyl cellulose, a carboxylic polymer,polyvinylpyrrolidone, dextrin, maltodextrin, polysaccharide, vinylidenechloride copolymer, starch, sodium lignosulfate, calcium lignosulfate,alginate, and polychloroprene; and the nutrient-absorbent bulking agentis preferably composed of at least two selected from the groupconsisting of: calcium bentonite, silica hydrogel, starch, a starchderivative, modified lignosulfonate, weathered coal, coal, activecarbon, zeolite, attapulgite, magnesium hydrogen phosphate trihydrate,sodium magnesium silicate, synthetic calcium silicate, vermiculite,humus, acrylate copolymer, silicon dioxide, activated clay,aluminosilicate, and sodium aluminosilicate.

In a preferred embodiment, the nutrient-absorbent supplement containsthe polymer in an amount of 0.1 to 50% by weight and thenutrient-absorbent bulking agent in an amount of 50 to 99.9% by weight,based on the total weight thereof. Further, the nutrient-absorbentbulking agent for use as a main component of the nutrient-absorbentsupplement contains an inorganic bulking agent and an organic bulkingagent with a weight ratio of 3:7 to 7:3 therebetween.

To give the nutrient-absorbent supplement, the mixture may be preferablydried at 80 to 100° C. for 20 min to 1 hr and the dried mixture ispreferably pulverized into a size of 150 meshes or lower.

Subsequently, the nutrient-absorbent supplement is blended with afertilizer ingredient. In this regard, the nutrient-absorbent supplementmay be preferably used in an amount of 5 to 25% by weight, based on theweight of the fertilizer ingredient.

In a preferred embodiment, the method for preparing a matrix-type,granular compound fertilizer may comprise i) homogeneously blending thenutrient-absorbent supplement with a fertilizer ingredient; ii)granulating the blend in a granulator to give granules; and iii) dryingthe granules.

The granulator may be a drum granulator or a pan granulator. The dryingstep may preferably be conducted at 300 to 450° C. for 30 to 40 min.

In accordance with another aspect thereof, the present inventionaddresses matrix-type, controlled-release granular compound fertilizerprepared by a method comprising: mixing a natural or synthetic polymeras a binder with a nutrient-absorbent bulking agent to give a mixture,and drying and pulverizing the mixture to afford a nutrient-absorbentsupplement; and evenly blending the nutrient-absorbent supplement with afertilizer ingredient and drying the blend.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 shows optical images of cut granules of a general compoundfertilizer (a) and the compound fertilizer (b) of the present inventionbefore and after treatment with distilled water; and

FIG. 2 shows optical images of particle phases of a general compoundfertilizer (a) and the compound fertilizer (b) of the present inventionbefore and after treatment with distilled water.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Below, a detailed description will be given of the present invention.

According to an aspect of the present invention there is provided amethod for preparing a matrix-type, controlled-release granular compoundfertilizer, comprising: mixing a natural or synthetic polymer as abinder with a nutrient-absorbent bulking agent to give a mixture, anddrying and pulverizing the mixture to afford a nutrient-absorbentsupplement; and evenly blending the nutrient-absorbent supplement with afertilizer ingredient and drying the blend.

Each step is described in detail as follows.

(1) Preparation of Nutrient-Absorbent Supplement

To afford a nutrient-absorbent supplement, a natural or syntheticpolymer as a binder is mixed with a nutrient-absorbent bulking agent,and then dried and pulverized.

Here, the natural or synthetic polymer serves to form, together with thenutrient-absorbent bulking agent, a matrix, and examples of the polymerinclude a combination of at least two selected from the group consistingof, but not limited to: polyacrylamide, polyvinylacetate, polyvinylacetate copolymer (-ethylene), polyvinyl alcohol and a polyvinyl alcoholcopolymer, ethyl cellulose, methyl cellulose, hydroxymethyl cellulose,hydroxypropyl cellulose, hydroxymethylpropyl cellulose, a carboxylicpolymer, polyvinylpyrrolidone, dextrin, maltodextrin, polysaccharide,vinylidene chloride copolymer, starch, sodium lignosulfate, calciumlignosulfate, alginate, and polychloroprene.

In addition, the nutrient-absorbent, bulking agent may be inorganicand/or organic bulking agents, and preferably a mixture of inorganic andorganic bulking agents. It is preferably composed of at least twoselected from the group consisting of, but not limited to: calciumbentonite, silica hydrogel, starch, a starch derivative, modifiedlignosulfonate, weathered coal, coal, active carbon, zeolite,attapulgite, magnesium hydrogen phosphate trihydrate, sodium magnesiumsilicate, synthetic calcium silicate, vermiculite, humus, acrylatecopolymer, silicon dioxide, activated clay, aluminosilicate, and sodiumaluminosilicate.

Based on the total weight of the supplement, the polymer is contained inan amount of 0.1 to 50% by weight, preferably in an amount of 1 to 40%by weight, and most preferably in an amount of 10 to 20% by weight. Thebulking agent is contained in an amount of 50 to 99.9% by weight,preferably in an amount of 60 to 99% by weight, and most preferably inan amount of 80 to 90% by weight, based on the total weight of thesupplement.

When used in an amount less than 0.1% by weight, the polymer cannot playa sufficient role as a binder in granulating the fertilizer. On theother hand, an amount of the polymer exceeding 50% by weight may degradenutrient absorption.

An inorganic bulking agent and an organic bulking agent may be usedalone, but preferable is a combination of inorganic and organic bulkingagents. In this context, an inorganic bulking agent may be preferablymixed at a weight ratio of 30:70 to 70:30 with an organic bulking agent,based on the total weight of the bulking agent.

In the preparation of the supplement, a mixture of the polymer and thebulking agent is dried at 80 to 100° C. for 20 min to 1 hr. Here, whenthe drying temperature is below 80° C., the raw materials are entangledduring mixing and pulverizing processes because of abundant water. Adrying temperature exceeding 100° C. may melt some of the mixture sothat it may act as a binder to generate agglomerates. In addition, whenthe mixture is dried for less than 20 min, the subsequent blendingprocess is difficult to perform because of a water content exceeding aproper level. More than 1 hour of drying may decrease thermalefficiency.

The dried, polymer and bulking agent mixture, that is, the supplement ispulverized into particles with a size of 150 meshes or less, preferably100 meshes or less, and most preferably 80 meshes. After beingpulverized to a predetermined size or less, the nutrient-absorbentsupplement can be evenly distributed over compound fertilizer granulesand thus can form a homogeneous matrix.

(2) Preparation of Compound Fertilizer with Nutrient-AbsorbentSupplement

Next, the nutrient-absorbent supplement and a fertilizer ingredient areevenly blended, and dried to obtain the matrix-type, granular compoundfertilizer. In this step, the supplement is evenly blended with afertilizer ingredient, and the blend is granulated using a drum or pangranulator, followed by drying the granules at 300 to 450° C. for 30 to40 min to form an intragranular microcapsule-type matrix.

To give a homogeneous blend, stirring is carried out at 50 to 100 rpmfor 4 to 10 min. Here, the nutrient-absorbent supplement may bepreferably blended in an amount of 5 to 25% by weight, based on thetotal weight of the fertilizer ingredient. When the supplement is usedin an amount less than 5% by weight, an intergranular matrix may bedifficult to form. More than 25% by weight of the supplement may notallow the nutrient to be released to the degree necessary for the earlygrowth stage of plants, inhibiting plant growth.

Subsequently, the homogeneous blend of the supplement and the fertilizeringredient is granulated. Here, the granulation may be preferablyconducted using a drum or pan granulator.

During granulation, steam or water is sprayed so that the polymer andthe fertilizer ingredient are dissolved, serving as a binder. By hot airafter the granulation, a polymer matrix is formed within granules, witha consequent increase in fineness modulus and hardness.

During the granulation, the inorganic and organic bulking agents and thepolymer within the supplement form a matrix in a network structure,increasing resistance to impact during packaging and transportation.

The granulated particles are dried at 300 to 450° C. for 30 to 40 min toform an intragranular microcapsule-type matrix. Here, when dried at lessthan 300° C., the compound fertilizer granules may be prone toundergoing water damage and compaction due to their high water content.On the other hand, drying at higher than 450° C. may carbonize theorganic bulking agent including the polymer to lower nutrientabsorption.

Finally, the matrix-type, controlled-release, granular compoundfertilizer is cooled, selected and packaged.

When applied to soil, the matrix-type, controlled-release granularcompound fertilizer absorbs water and dissolves. The dissolvedfertilizer ingredient is absorbed by and retained within the absorbentorganic and inorganic bulking agents by electrostatic attraction. Inaddition, the fertilizer ingredients permeate soil pores as thefertilizer granules absorb water and collapse due to the nutrientabsorption (electrostatic attraction) and water retention capacity ofthe polymer itself. Interaction of soil-fertilizer-bulking agent-polymerallows for the formation of a microcapsular matrix.

Typical fertilizer ingredients in this art may be available in thepresent invention. Examples of the fertilizer ingredient useful in thepresent invention include, but are not limited to: urea, ammoniumsulfate, ammonium phosphate, potassium chloride, and siliceous.

A matrix-type, controlled-release granular fertilizer can be prepared ina single process where supplement preparation and compound fertilizerpreparation are not divided clearly, as well as by the above-mentionedmethod.

Further, in order to meet nutrient requirements by plant, thecontrolled-release granular compound fertilizer may be blended withcoated fertilizer having a certain dissolution time.

Furthermore, in order to more accurately meet nutrient requirements byplant, the controlled-release granular compound fertilizer may beblended with coated fertilizer having a certain dissolution time, and amicroorganism having the ability to fix nitrogen and to dissolvephosphoric acid and potassium.

A better understanding of the present invention may be obtained throughthe following examples which are set forth to illustrate, but are not tobe construed as limiting the present invention.

Preparation Example 1

Preparation of Nutrient-Absorbent Supplement

A mixture of 50% by weight of an inorganic bulking agent (vermiculite)and 40% by weight of an organic bulking agent (humus) was homogeneouslycombined with a 4.9% by weight of sodium lignosulfonate, 0.1% by weightof polyacrylamide, and 5% by weight of hydroxypropylmethyl cellulose at50 rpm for 10 min. The resulting mixture was dried at about 90° C. for40 min, followed by pulverization into granules with a size of 80 meshesor less.

Example 1

Preparation of Matrix-Type, Controlled-Release Granular CompoundFertilizer

10% by weight of the nutrient-absorbent supplement obtained inPreparation Example 1 was blended with 10% by weight of urea, 40% byweight of ammonium sulfate, 14% by weight of ammonium phosphate, 12% byweight of potassium chloride, and 14% by weight of siliceous, and theblend was granulated using a pan granulator. Subsequently, the granuleswere dried at 400° C. for 30 min to form granular compound fertilizerwith an intragranular microcapsule-type matrix.

Example 2

10% by weight of the nutrient-absorbent supplement obtained inPreparation Example 1 was blended with 18% by weight of urea, 37% byweight of ammonium sulfate, 14% by weight of ammonium phosphate, 14% byweight of potassium chloride, and 7% by weight of siliceous, and theblend was granulated using a pan granulator. Subsequently, the granuleswere dried at 400° C. for 30 min to form granular compound fertilizerwith an intragranular microcapsule-type matrix.

Comparative Example 1

Preparation of General Compound Fertilizer

10% by weight of bentonite, 18% by weight of urea, 37% by weight ofammonium sulfate, 14% by weight of ammonium phosphate, 14% by weight ofpotassium chloride, and 7% by weight of siliceous were blended, andgranulated using a pan granulator to afford a compound fertilizer.

Test Example 1

Granules of both the compound fertilizer prepared in Example 1(polymer+inorganic bulking agent+organic bulking agent+fertilizer) andthe general compound fertilizer of Comparative Example 1 (bulkingagent+fertilizer) were examined for binding state therebetween beforeand after treatment with distilled water, and were observed under anoptical microscope (Nikon Eclipse 50i, ×2000). Images are given in FIGS.1 and 2.

FIG. 1 shows cut granules of a general compound fertilizer (a) and thecompound fertilizer (b) of the present invention before and aftertreatment with distilled water. FIG. 2 shows particle phases of ageneral compound fertilizer (a) and the compound fertilizer (b) of thepresent invention before and after treatment with distilled water.

As can be seen in FIGS. 1 and 2, a network is formed in the granules ofthe compound fertilizer of the present invention.

Test Example 2

Comparison of Leaching Suppression

The matrix-type granular compound fertilizer of Example 1 and thegeneral compound fertilizer of Comparative Example 1 were assayed forleaching suppression ability, and the results are given in Table 1,below.

Assay for leaching suppression ability: In a cylindrical column long13.5 cm with a diameter of 2.6 cm, three sheets of No. 2 filter paperwere placed on the bottom and 10 g of sand was then loaded thereto.Again, one sheet of No. 2 filter paper was laid on the sand, followed byloading a mixture of 30 g of soil and a fertilizer sample of Example 1or Comparative Example 1 (0.5 g and 1 g each) to the sand. Subsequently,one sheet of No. 2 filter paper was placed on the mixture, and 60 ml ofwater was slowly added from the top. When water reached a cork portion,the column was fastened with the cork. After 12 hrs, the cork was openedand the time taken for the fertilizer to leach to the soil layers wasmeasured.

TABLE 1 Ex. 1 C. Ex. 1 Soil 0.5 g 1 g 0.5 g 1 g Leaching time (min) 100290 6,480 180 660 Leaching suppression % relative to 0 190 6,380 80 560non-treated control Leaching suppression % relative to 61.1 881.8general compound fertilizer

From the data of Table 1, it is understood that the leaching suppressionpotential of the matrix-type granular compound fertilizer according tothe present invention is far superior to that of the general compoundfertilizer.

Test Example 3

Effect of Matrix-Type, Controlled-Release Granular Compound Fertilizeron Plant Growth

1. Material and Method

Main Materials:

Example 1—matrix-type, controlled-release granular compound fertilizer

Example 2—matrix-type, controlled-release granular compound fertilizer

Comparative Example 1—Conventional slow-releasing fertilizer

-   -   Test plant: rice (cultivar: Akibare)    -   Test method: compound fertilizers of Examples 1 and 2 were        applied to soil 4 days before transplantation, and the soil was        overturned using a rotary tiller so that the fertilizers were        evenly distributed in the soil. The amount of applied fertilizer        was, on the basis of 10a, 73.3 kg for Example 1, 61.1 kg for        Example 2, and 61.1 kg for Comparative Example 1. The        predetermined amounts of fertilizers were applied once before        transplantation. Growth was examined twice by growth stage.

Measurement was made of plant height, number of tillers, and leaf color(SPAD value), and cultivation was conducted according to the standardcultural practices for rice of the Korean Rural DevelopmentAdministration.

2. Result

Overall plant growth was evaluated in terms of plant height, leaf color,and number of tillers on day 30 and 60 after the application of thecompound fertilizers of Examples 1 and 2 and the conventionalslow-releasing fertilizer of Comparative Example 1, and the results aresummarized in Table 2, below. As is understood from the data of Table 2,comparable results of plant height, leaf color and number of tillerswere detected between the fertilizers of Examples and ComparativeExample 1. Further, the fertilizers of Examples 1 and 2 were found tohave continuously maintained their fertilizing effect even whenpredetermined amounts of them were applied at once as a base fertilizer.

TABLE 2 Item Day 30 after Day 60 after transplantation transplantationNo C. No C. Fertilizer Ex. 1 Ex. 1 Ex. 2 Fertilizer Ex. 1 Ex. 1 Ex. 2Round Amount of applied fertilizer (/10a) No. 0 kg 61.1 kg 73.3 kg 61.1kg 0 kg 61.1 kg 73.3 kg 61.1 g Plant 1 31.1 35.5 36.1 36.4 61.2 70.569.8 73.5 Height 2 29.5 36.5 35.3 36.1 62.5 72.6 73.2 70.6 (cm) 3 32.536.1 35.6 35.7 62.8 73.5 71.2 71.5 Avg. 31.0 36.0 35.7 36.1 62.2 72.271.4 71.9 Leaf color 1 27.5 40.5 40.8 42.6 23.4 33.5 32.9 33.5 SPADvalue 2 26.7 41.8 41.6 42.1 22.1 34.6 35.1 34.1 3 25.6 42.1 42.5 42.721.5 34.1 34.8 34.2 Avg. 26.6 41.5 41.6 42.5 22.3 34.1 34.3 33.9 No of 114 20 23 22 12 21 22 20 Tillers 2 13 22 22 20 13 20 20 19 (ea.) 3 13 2121 22 12 20 21 22 Avg. 13.3 21.0 22.0 21.3 12.3 20.3 21.0 20.3

Test Example 4

Effect of Matrix-Type, Controlled-Release Granular Compound Fertilizeron Pepper Plant Growth

1. Material and Method

Main Materials:

Example 1—matrix-type, controlled-release granular compound fertilizer

Example 2—matrix-type, controlled-release granular compound fertilizer

Comparative Example 1—Conventional slow-releasing fertilizer

-   -   Test plant: pepper (cultivar: Buchon)    -   Test method: compound fertilizers of Examples 1 and 2 were        applied to soil 7 days before transplantation and the soil was        overturned using a rotary tiller so that the fertilizers were        evenly distributed in the soil. The amount of applied fertilizer        was, on the basis of 10a, 126.63 kg for Example 1, 105.5 kg for        Example 2, and 105.5 kg for Comparative Example 1. The        predetermined amounts of fertilizers were applied once before        transplantation. Growth was examined three times by growth        stage, and the fruits were counted finally upon harvest.

Measurement was made of plant height, leaf color (SPAD value), yield perarea, and cultivation was conducted according to the standard culturalpractices for pepper of the Korean Rural Development Administration.

2. Result

Overall plant growth was evaluated in terms of plant height and leafcolor on day 10 and 20 after the application of the compound fertilizersof Examples 1 and 2 and the conventional slow-releasing fertilizer ofComparative Example 1, and the results are summarized in Table 3, below.As is understood from the data of Table 3, the fertilizers of Examples 1and 2 guaranteed superiority in plant height and leaf color, compared tothat of Comparative Example 1, and with the highest total yield ofpepper fruits was obtained with the fertilizer of Example 2. Further,the fertilizers of Examples 1 and 2 were found to continuously maintaintheir fertilizing effect even when predetermined amounts were applied atonce as a base fertilizer.

TABLE 3 Item Plant Height (cm) Leaf Color (SPAD value) No No fertilizerC. Ex. 1 Ex. 1 Ex. 2 fertilizer C. Ex. 1 Ex. 1 Ex. 2 Round Amount ofApplied Fertilizer (/10a) No. 0 kg 105.5 kg 126.6 kg 105.5 kg 0 kg 105.5kg 126.6 kg 105.5 kg 10 Days 1 13.2 16.2 17.8 17.1 28.5 45.7 47.5 47.5after 2 12.5 15.9 18.2 17.6 29.4 46.5 46.7 47.1 Transplantation 3 12.815.3 18.1 17.3 28.4 46.1 46.4 47.3 Avg. 12.8 15.8 18.0 17.3 28.8 46.146.9 47.3 20 Days 1 18.5 24.5 23.8 24.1 38.5 63.2 67.1 67.1 After 2 17.423.2 23.7 22.1 38.1 62.1 65.4 66.7 Transplantation 3 17.5 23.9 22.5 23.837.2 61.4 66.6 66.9 Avg. 17.8 23.9 23.3 23.3 37.9 62.2 66.4 66.9 30 Days1 31.2 36.8 35.7 37.5 39.4 66.7 69.4 71.1 After 2 32.4 37.1 37.2 37.140.1 66.4 71.4 69.5 Transplantation 3 31.6 37.4 37.3 36.5 41.8 66.5 71.470.1 Avg. 31.7 37.1 36.7 37.0 40.4 66.5 70.7 70.2

TABLE 4 Round No Item No fertilizer C. Ex. 1 Ex. 1 Ex. 2 Amount of 0 kg105.5 kg 126.6 kg 105.5 kg applied fertilizer (/10a) Fresh weight of 14.1 8.4 6.2 7.5 red pepper 2 3.8 6.3 6.2 7.0 (kg/30 m²) 3 4.7 7.2 9.09.5 Total 12.6 21.9 21.4 24.0

Because the compound fertilizer according to the present inventionretains nutrients therein, without loss even after application to soil,no additional applications are needed during the overall growth periodof plants, which is helpful in reducing work in areas with a shortage offarm labor. In addition, it's possible to apply the compound fertilizerto sideland placement and thus makes a contribution to farmmechanization.

Conventional controlled-release, polymer-coated fertilizer or chemicallycontrolled-release fertilizer, such as UF, CDU and IBDU, imparts a greateconomic burden to consumers because it requires a complex process forpreparation thereof, and employs expensive raw materials. In contrast,the controlled-release fertilizer enjoys the advantage of being suppliedat a low cost, not only because its preparation process is simple enoughto employ general production processes of fertilizer, but also becauseits raw materials are cheap.

Although the preferred embodiments of the present invention have beendisclosed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims.

What is claimed is:
 1. A method for preparing matrix-type,controlled-release granular compound fertilizer, consisting essentiallyof: mixing a natural or synthetic polymer as a binder with anutrient-absorbent bulking agent to give a mixture, wherein the polymeris composed of at least two polymers selected from the group consistingof: polyacrylamide, polyvinylacetate, polyvinyl acetate copolymer(-ethylene), polyvinyl alcohol and a polyvinyl alcohol copolymer, ethylcellulose, methyl cellulose, hydroxymethyl cellulose, hydroxypropylcellulose, hydroxymethylpropyl cellulose, a carboxylic polymer,polyvinylpyrrolidone, dextrin, maltodextrin, polysaccharide, vinylidenechloride copolymer, starch, sodium lignosulfate, calcium lignosulfate,alginate, and polychloroprene, and wherein the nutrient-absorbentbulking agent is composed of at least two bulking agents selected fromthe group consisting of calcium bentonite, silica hydrogel, starch, astarch derivative, modified lignosulfonate, weathered coal, coal, activecarbon, zeolite, attapulgite, magnesium hydrogen phosphate trihydrate,sodium magnesium silicate, synthetic calcium silicate, vermiculite,humus, acrylate copolymer, silicon dioxide, activated clay,aluminosilicate, and sodium aluminosilicate, and drying and pulverizingthe mixture to afford a nutrient-absorbent supplement; and homogeneouslyblending the nutrient-absorbent supplement with a fertilizer ingredient,granulating the blend in a granulator to form granules, and drying thegranules, wherein the drying is conducted at 300 to 450 degrees Celsiusfor 30 to 40 minutes.
 2. The method of claim 1, wherein thenutrient-absorbent supplement contains the polymer in an amount of 0.1to 50% by weight, and the bulking agent in an amount of 50 to 99.9% byweight, based on a total weight thereof.
 3. The method of claim 1,wherein the nutrient-absorbent bulking agent comprises a mixture of aninorganic bulking agent at a weight ratio of 3:7 to 7:3 with an organicbulking agent.
 4. The method of claim 1, wherein the mixture for thesupplement is dried for 20 min to 1 hr at 80 to 100° C.
 5. The method ofclaim 1, wherein the mixture is pulverized into particles with a size of150 meshes or less.
 6. The method of claim 1, wherein thenutrient-absorbent supplement is blended in an amount of 5 to 25% byweight, based on a total weight of the fertilizer ingredient.
 7. Themethod of claim 1, wherein the fertilizer ingredient is selected fromthe group consisting of: urea, ammonium sulfate, ammonium phosphate,potassium chloride and siliceous fertilizer.
 8. A method for preparing amatrix-type, granular compound fertilizer, comprising: i) homogeneouslyblending the nutrient-absorbent supplement of claim 1 with a fertilizeringredient; ii) granulating the blend in a granulator to give granules;and iii) drying the granules, wherein the drying is conducted at 300 to450 degrees Celsius for 30 to 40 minutes.
 9. The method of claim 8,wherein the granulator is a drum granulator or a pan granulator.
 10. Amatrix-type, controlled-release granular compound fertilizer, preparedusing the method of claim 1.